/* ============================================================
   Feiyu Yao — Personal Site
   Academic-modern, deep ink blue accent
   ============================================================ */

:root {
  /* Light */
  --bg:        oklch(0.985 0.004 80);
  --bg-2:      oklch(0.965 0.006 80);
  --bg-3:      oklch(0.945 0.008 80);
  --ink:       oklch(0.18 0.008 260);
  --ink-2:     oklch(0.36 0.01 260);
  --ink-3:     oklch(0.56 0.012 260);
  --rule:      oklch(0.89 0.006 80);
  --rule-2:    oklch(0.82 0.008 80);
  --accent:    oklch(0.38 0.12 260);
  --accent-2:  oklch(0.48 0.13 260);
  --accent-wash: oklch(0.95 0.03 260);

  --serif: "Newsreader", ui-serif, Georgia, "Times New Roman", serif;
  --sans:  "Inter", ui-sans-serif, system-ui, -apple-system, "Helvetica Neue", Arial, sans-serif;
  --mono:  "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;

  --maxw: 1120px;
  --gutter: clamp(24px, 5vw, 56px);

  --ease: cubic-bezier(.2,.7,.2,1);
}

:root[data-theme="dark"] {
  --bg:        oklch(0.14 0.008 260);
  --bg-2:      oklch(0.18 0.01 260);
  --bg-3:      oklch(0.22 0.012 260);
  --ink:       oklch(0.96 0.004 80);
  --ink-2:     oklch(0.82 0.006 80);
  --ink-3:     oklch(0.62 0.008 80);
  --rule:      oklch(0.28 0.012 260);
  --rule-2:    oklch(0.36 0.014 260);
  --accent:    oklch(0.78 0.12 260);
  --accent-2:  oklch(0.68 0.13 260);
  --accent-wash: oklch(0.24 0.04 260);
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
html { scroll-behavior: smooth; }

body {
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  font-feature-settings: "ss01", "cv11";
  transition: background .35s var(--ease), color .35s var(--ease);
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; text-decoration-thickness: 1px; }

img { max-width: 100%; display: block; }

/* ---------- Nav ---------- */

.nav {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in oklch, var(--bg) 92%, transparent);
  backdrop-filter: saturate(1.2) blur(10px);
  -webkit-backdrop-filter: saturate(1.2) blur(10px);
  border-bottom: 1px solid var(--rule);
}
.nav-inner {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 14px var(--gutter);
  display: flex; align-items: center; gap: 28px;
}
.brand {
  font-family: var(--serif);
  font-weight: 500;
  font-size: 18px;
  letter-spacing: -0.01em;
  color: var(--ink);
  display: flex; align-items: baseline; gap: 10px;
}
.brand .brand-dot {
  display: inline-block;
  width: 7px; height: 7px; border-radius: 50%;
  background: var(--accent);
  transform: translateY(-2px);
}
.brand-sub {
  font-family: var(--mono);
  font-size: 11px;
  color: var(--ink-3);
  letter-spacing: 0.02em;
}

.nav-links {
  display: flex; gap: 4px; margin-left: auto;
  align-items: center;
}
.nav-link {
  font-size: 13.5px;
  color: var(--ink-2);
  padding: 8px 12px;
  border-radius: 6px;
  position: relative;
  transition: color .2s var(--ease), background .2s var(--ease);
}
.nav-link:hover { color: var(--ink); text-decoration: none; background: var(--bg-2); }
.nav-link.active { color: var(--ink); }
.nav-link.active::after {
  content: "";
  position: absolute;
  left: 12px; right: 12px; bottom: 2px;
  height: 1.5px; background: var(--accent);
}

.nav-tools {
  display: flex; gap: 6px; align-items: center;
  padding-left: 14px; margin-left: 6px;
  border-left: 1px solid var(--rule);
}

.icon-btn {
  width: 32px; height: 32px;
  display: inline-flex; align-items: center; justify-content: center;
  border: 1px solid var(--rule);
  background: transparent;
  color: var(--ink-2);
  border-radius: 6px;
  cursor: pointer;
  transition: all .2s var(--ease);
  font-family: var(--mono);
  font-size: 12px;
  padding: 0;
}
.icon-btn:hover { color: var(--ink); border-color: var(--rule-2); background: var(--bg-2); }
.icon-btn svg { width: 14px; height: 14px; }

.variation-toggle {
  display: flex; border: 1px solid var(--rule); border-radius: 6px;
  padding: 2px; gap: 2px; background: var(--bg-2);
}
.variation-toggle button {
  border: 0; background: transparent;
  font-family: var(--mono); font-size: 11px;
  color: var(--ink-3);
  padding: 5px 10px;
  border-radius: 4px;
  cursor: pointer;
  letter-spacing: 0.04em;
}
.variation-toggle button.active {
  background: var(--bg);
  color: var(--ink);
  box-shadow: 0 1px 2px rgba(0,0,0,.04);
}

/* ---------- Layout ---------- */

main { min-height: 60vh; }
.page {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: clamp(40px, 6vw, 72px) var(--gutter) 120px;
  animation: pageIn .4s var(--ease);
}
@keyframes pageIn {
  from { opacity: 0; transform: translateY(6px); }
  to   { opacity: 1; transform: translateY(0); }
}

/* ---------- Type ---------- */

.eyebrow {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--ink-3);
  display: inline-flex; align-items: center; gap: 8px;
}
.eyebrow::before {
  content: "";
  display: inline-block;
  width: 18px; height: 1px;
  background: var(--ink-3);
}

h1, h2, h3, h4 { color: var(--ink); margin: 0; }
h1.display {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(44px, 6vw, 72px);
  line-height: 1.02;
  letter-spacing: -0.025em;
}
h1.display em {
  font-style: italic;
  color: var(--accent);
}
h2.section {
  font-family: var(--serif);
  font-weight: 500;
  font-size: clamp(26px, 3vw, 34px);
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: 4px;
}
h3 {
  font-family: var(--sans);
  font-weight: 600;
  font-size: 15.5px;
  line-height: 1.35;
}

.lede {
  font-family: var(--serif);
  font-size: clamp(18px, 1.6vw, 21px);
  line-height: 1.55;
  color: var(--ink-2);
  font-weight: 380;
  letter-spacing: -0.005em;
  max-width: 62ch;
}

.prose p { color: var(--ink-2); }
.prose p + p { margin-top: 12px; }

.rule {
  height: 1px;
  background: var(--rule);
  border: 0;
  margin: 48px 0;
}

/* ---------- Hero ---------- */

.hero {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: clamp(32px, 5vw, 72px);
  align-items: center;
  padding-top: clamp(40px, 6vw, 64px);
  padding-bottom: clamp(40px, 6vw, 64px);
}
.hero-body > * + * { margin-top: 20px; }
.hero-meta {
  display: flex; flex-wrap: wrap;
  gap: 16px 28px;
  font-family: var(--mono); font-size: 12px; color: var(--ink-3);
  letter-spacing: 0.01em;
  padding-top: 8px;
}
.hero-meta span { display: inline-flex; align-items: center; gap: 8px; }
.hero-meta .dot {
  width: 4px; height: 4px; border-radius: 50%;
  background: var(--accent);
}
.hero-portrait {
  aspect-ratio: 4/5;
  border-radius: 2px;
  background: var(--bg-2);
  border: 1px solid var(--rule);
  position: relative;
  overflow: hidden;
}
.hero-portrait .placeholder {
  position: absolute; inset: 0;
  background-image:
    repeating-linear-gradient(135deg,
      transparent 0 9px,
      color-mix(in oklch, var(--ink-3) 10%, transparent) 9px 10px);
  display: flex; align-items: flex-end; justify-content: flex-start;
  padding: 16px;
}
.hero-portrait .placeholder span {
  font-family: var(--mono); font-size: 10px;
  color: var(--ink-3); letter-spacing: 0.08em;
  text-transform: uppercase;
  background: var(--bg); padding: 4px 7px;
  border: 1px solid var(--rule);
}

/* variation B hero - bigger, different proportions */
.hero.v-b {
  grid-template-columns: 1fr;
  text-align: left;
  padding-top: clamp(56px, 8vw, 96px);
}
.hero.v-b .hero-portrait { display: none; }
.hero.v-b h1.display { font-size: clamp(52px, 8vw, 96px); }

/* ---------- Home sections ---------- */

.home-grid {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: clamp(32px, 5vw, 72px);
  padding: 44px 0;
  border-top: 1px solid var(--rule);
}
.home-grid .label {
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--ink-3);
  padding-top: 6px;
}

.now-list { list-style: none; padding: 0; margin: 0; }
.now-list li {
  display: grid;
  grid-template-columns: 110px 1fr;
  gap: 20px;
  padding: 14px 0;
  border-bottom: 1px dashed var(--rule);
  align-items: baseline;
}
.now-list li:last-child { border-bottom: 0; }
.now-list .when {
  font-family: var(--mono); font-size: 11.5px;
  color: var(--ink-3); letter-spacing: 0.02em;
}
.now-list .what strong { color: var(--ink); font-weight: 600; font-size: 15px; }
.now-list .what p { margin: 4px 0 0; color: var(--ink-2); font-size: 14px; line-height: 1.55; }

/* Featured paper (home) */
.featured-paper {
  display: grid;
  grid-template-columns: 180px 1fr;
  gap: 28px;
  padding: 24px;
  border: 1px solid var(--rule);
  background: var(--bg-2);
  border-radius: 2px;
  align-items: start;
  position: relative;
}
.featured-paper::before {
  content: "FEATURED";
  position: absolute; top: -1px; left: 24px;
  transform: translateY(-50%);
  font-family: var(--mono); font-size: 10px;
  letter-spacing: 0.12em;
  background: var(--bg); padding: 2px 8px;
  color: var(--accent); border: 1px solid var(--rule);
}
.paper-thumb {
  aspect-ratio: 3/4;
  background: var(--bg-3);
  border: 1px solid var(--rule);
  display: flex; align-items: center; justify-content: center;
  position: relative;
  overflow: hidden;
}
.paper-thumb::before {
  content: "";
  position: absolute; inset: 0;
  background-image:
    repeating-linear-gradient(45deg,
      transparent 0 6px,
      color-mix(in oklch, var(--ink-3) 8%, transparent) 6px 7px);
}
.paper-thumb span {
  position: relative;
  font-family: var(--mono); font-size: 9.5px;
  color: var(--ink-3);
  background: var(--bg); padding: 3px 6px;
  border: 1px solid var(--rule);
  letter-spacing: 0.06em;
}
.featured-paper h3 {
  font-family: var(--serif);
  font-weight: 500;
  font-size: 22px;
  line-height: 1.25;
  letter-spacing: -0.015em;
  margin-bottom: 10px;
}
.venue-badge {
  display: inline-block;
  font-family: var(--mono); font-size: 10.5px;
  letter-spacing: 0.08em;
  padding: 3px 8px;
  border: 1px solid var(--accent);
  color: var(--accent);
  border-radius: 2px;
  margin-bottom: 12px;
}
.authors {
  font-size: 13.5px;
  color: var(--ink-2);
  line-height: 1.5;
}
.authors .me {
  color: var(--ink);
  font-weight: 600;
}
.paper-links {
  display: flex; gap: 14px; margin-top: 14px;
  font-family: var(--mono); font-size: 11.5px;
  letter-spacing: 0.04em;
}
.paper-links a {
  color: var(--ink-2);
  display: inline-flex; align-items: center; gap: 4px;
  padding: 4px 0;
  border-bottom: 1px solid var(--rule-2);
}
.paper-links a:hover { color: var(--accent); border-bottom-color: var(--accent); text-decoration: none; }

/* ---------- Publications list ---------- */

.pub-year {
  display: flex; align-items: baseline; gap: 20px;
  padding: 40px 0 14px;
  border-bottom: 1px solid var(--rule);
}
.pub-year .year {
  font-family: var(--serif);
  font-weight: 400;
  font-size: 36px;
  letter-spacing: -0.02em;
  color: var(--ink);
}
.pub-year .count {
  font-family: var(--mono); font-size: 11px;
  color: var(--ink-3); letter-spacing: 0.08em;
}

.pub {
  display: grid;
  grid-template-columns: 110px 1fr;
  gap: 28px;
  padding: 22px 0;
  border-bottom: 1px solid var(--rule);
  align-items: start;
  transition: background .25s var(--ease);
}
.pub:hover { background: color-mix(in oklch, var(--accent-wash) 60%, transparent); }
.pub .venue {
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.06em;
  color: var(--accent);
  padding-top: 3px;
}
.pub .venue .year-small {
  display: block;
  color: var(--ink-3);
  margin-top: 2px;
  font-size: 10.5px;
}
.pub h3.title {
  font-family: var(--serif);
  font-weight: 500;
  font-size: 19px;
  line-height: 1.3;
  letter-spacing: -0.01em;
  margin-bottom: 6px;
  color: var(--ink);
}
.pub .authors { font-size: 13.5px; }
.pub .pub-links { margin-top: 10px; }

/* Variation B: card style */
.pub-card {
  display: grid;
  grid-template-columns: 160px 1fr auto;
  gap: 24px;
  padding: 22px;
  border: 1px solid var(--rule);
  background: var(--bg);
  border-radius: 2px;
  margin-bottom: 14px;
  transition: all .25s var(--ease);
  align-items: start;
}
.pub-card:hover {
  border-color: var(--rule-2);
  transform: translateY(-1px);
  box-shadow: 0 6px 20px -10px color-mix(in oklch, var(--ink) 20%, transparent);
}
.pub-card h3.title {
  font-family: var(--serif);
  font-weight: 500;
  font-size: 20px;
  line-height: 1.25;
  letter-spacing: -0.01em;
  margin-bottom: 10px;
}
.pub-card-meta {
  text-align: right;
  font-family: var(--mono); font-size: 11px;
  color: var(--ink-3);
  letter-spacing: 0.06em;
  padding-top: 3px;
  min-width: 80px;
}
.pub-card-meta .venue-strong { color: var(--accent); display: block; margin-bottom: 4px; }

/* ---------- Projects ---------- */

.project-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 28px;
  margin-top: 40px;
}
@media (max-width: 800px) { .project-grid { grid-template-columns: 1fr; } }

.project-card {
  border: 1px solid var(--rule);
  background: var(--bg);
  border-radius: 2px;
  overflow: hidden;
  transition: all .3s var(--ease);
  display: flex; flex-direction: column;
}
.project-card:hover {
  border-color: var(--rule-2);
  transform: translateY(-2px);
  box-shadow: 0 14px 40px -20px color-mix(in oklch, var(--ink) 25%, transparent);
}
.project-thumb {
  aspect-ratio: 16/10;
  background: var(--bg-2);
  border-bottom: 1px solid var(--rule);
  position: relative;
  overflow: hidden;
}
.project-thumb::after {
  content: "";
  position: absolute; inset: 0;
  background-image:
    repeating-linear-gradient(20deg,
      transparent 0 10px,
      color-mix(in oklch, var(--ink-3) 10%, transparent) 10px 11px);
}
.project-thumb .tag {
  position: absolute; top: 14px; left: 14px; z-index: 1;
  font-family: var(--mono); font-size: 10px;
  letter-spacing: 0.1em;
  color: var(--ink);
  background: var(--bg);
  border: 1px solid var(--rule);
  padding: 4px 8px;
}
.project-thumb .label {
  position: absolute; bottom: 14px; right: 14px; z-index: 1;
  font-family: var(--mono); font-size: 10px;
  letter-spacing: 0.08em;
  color: var(--ink-3);
  background: var(--bg);
  border: 1px solid var(--rule);
  padding: 4px 8px;
  text-transform: uppercase;
}
.project-body {
  padding: 22px 24px 26px;
  flex: 1;
  display: flex; flex-direction: column;
}
.project-body h3 {
  font-family: var(--serif);
  font-weight: 500;
  font-size: 21px;
  letter-spacing: -0.01em;
  line-height: 1.2;
  margin-bottom: 10px;
}
.project-body p { color: var(--ink-2); font-size: 14px; line-height: 1.6; flex: 1; }
.project-footer {
  display: flex; justify-content: space-between; align-items: center;
  font-family: var(--mono); font-size: 11px;
  letter-spacing: 0.04em;
  color: var(--ink-3);
  margin-top: 16px;
  padding-top: 14px;
  border-top: 1px dashed var(--rule);
}
.project-footer .arrow {
  color: var(--accent);
  transition: transform .25s var(--ease);
}
.project-card:hover .project-footer .arrow { transform: translateX(3px); }

/* Variation B: editorial list */
.project-list .project-row {
  display: grid;
  grid-template-columns: 40px 1fr 180px 120px;
  gap: 24px;
  padding: 22px 0;
  border-bottom: 1px solid var(--rule);
  align-items: baseline;
  transition: background .2s var(--ease);
}
.project-list .project-row:hover { background: color-mix(in oklch, var(--accent-wash) 50%, transparent); }
.project-list .num {
  font-family: var(--mono); font-size: 11px;
  color: var(--ink-3); letter-spacing: 0.04em;
}
.project-list h3 {
  font-family: var(--serif);
  font-weight: 500;
  font-size: 20px;
  letter-spacing: -0.01em;
}
.project-list .desc { color: var(--ink-2); font-size: 13.5px; margin-top: 4px; line-height: 1.5; }
.project-list .tags { font-family: var(--mono); font-size: 11px; color: var(--ink-3); }
.project-list .tags .pill {
  border: 1px solid var(--rule);
  padding: 2px 6px;
  margin-right: 4px;
  display: inline-block;
}
.project-list .link {
  font-family: var(--mono); font-size: 11px;
  color: var(--accent);
  letter-spacing: 0.04em;
  text-align: right;
}

@media (max-width: 800px) {
  .project-list .project-row {
    grid-template-columns: 40px 1fr;
    row-gap: 8px;
  }
  .project-list .tags, .project-list .link { grid-column: 2; }
}

/* ---------- CV ---------- */

.cv-section { margin-bottom: 48px; }
.cv-row {
  display: grid;
  grid-template-columns: 160px 1fr;
  gap: 28px;
  padding: 16px 0;
  border-bottom: 1px dashed var(--rule);
  align-items: start;
}
.cv-row:last-child { border-bottom: 0; }
.cv-row .when {
  font-family: var(--mono); font-size: 12px;
  color: var(--ink-3); letter-spacing: 0.02em;
  padding-top: 3px;
}
.cv-row strong { font-weight: 600; color: var(--ink); font-size: 15px; }
.cv-row .place {
  font-family: var(--mono); font-size: 11.5px;
  color: var(--accent); letter-spacing: 0.02em;
  margin-left: 8px;
}
.cv-row p { margin: 6px 0 0; color: var(--ink-2); font-size: 14px; }

.award-group { margin-bottom: 20px; }
.award-group h4 {
  font-family: var(--mono); font-size: 11px;
  text-transform: uppercase; letter-spacing: 0.1em;
  color: var(--ink-3);
  margin: 0 0 10px;
  font-weight: 500;
}
.award-group ul { list-style: none; padding: 0; margin: 0; }
.award-group li {
  padding: 6px 0;
  color: var(--ink-2);
  font-size: 14px;
  line-height: 1.5;
  display: grid;
  grid-template-columns: 60px 1fr;
  gap: 20px;
}
.award-group li .yr { font-family: var(--mono); font-size: 11.5px; color: var(--ink-3); }

/* ---------- Personal ---------- */

.personal {
  padding: 48px 0;
  border-top: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
}
.personal-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 28px;
  margin-top: 28px;
}
@media (max-width: 700px) { .personal-grid { grid-template-columns: 1fr; } }
.personal-card {
  aspect-ratio: 4/3;
  background: var(--bg-2);
  border: 1px solid var(--rule);
  position: relative;
  overflow: hidden;
}
.personal-card::before {
  content: "";
  position: absolute; inset: 0;
  background-image:
    repeating-linear-gradient(60deg,
      transparent 0 8px,
      color-mix(in oklch, var(--ink-3) 10%, transparent) 8px 9px);
}
.personal-card .caption {
  position: absolute;
  bottom: 14px; left: 14px;
  font-family: var(--mono); font-size: 11px;
  color: var(--ink);
  background: var(--bg);
  border: 1px solid var(--rule);
  padding: 5px 9px;
  letter-spacing: 0.04em;
  z-index: 1;
}
.personal-card .kicker {
  position: absolute;
  top: 14px; right: 14px;
  font-family: var(--mono); font-size: 10px;
  letter-spacing: 0.1em; text-transform: uppercase;
  color: var(--ink-3);
  z-index: 1;
}

/* ---------- Footer ---------- */

footer.site {
  border-top: 1px solid var(--rule);
  padding: 36px var(--gutter);
  max-width: var(--maxw);
  margin: 40px auto 0;
  display: flex; justify-content: space-between;
  font-family: var(--mono); font-size: 11.5px;
  color: var(--ink-3);
  letter-spacing: 0.02em;
  flex-wrap: wrap; gap: 16px;
}
footer.site a { color: var(--ink-3); }
footer.site a:hover { color: var(--accent); text-decoration: none; }

/* ---------- Responsive ---------- */
@media (max-width: 820px) {
  .hero { grid-template-columns: 1fr; }
  .hero-portrait { max-width: 260px; }
  .home-grid { grid-template-columns: 1fr; gap: 16px; }
  .featured-paper { grid-template-columns: 1fr; }
  .paper-thumb { max-width: 200px; }
  .pub { grid-template-columns: 1fr; gap: 8px; }
  .pub-card { grid-template-columns: 1fr; }
  .pub-card-meta { text-align: left; }
  .cv-row { grid-template-columns: 1fr; gap: 4px; }
  .nav-inner { gap: 12px; flex-wrap: wrap; }
  .nav-links { gap: 0; margin-left: 0; width: 100%; order: 2; justify-content: flex-start; }
  .nav-tools { margin-left: auto; }
}

/* ---------- Utility ---------- */
.sr-only { position:absolute; width:1px; height:1px; padding:0; margin:-1px; overflow:hidden; clip:rect(0,0,0,0); border:0; }

/* ---------- Scholar badge ---------- */
.scholar {
  display: inline-flex; gap: 16px;
  padding: 12px 16px;
  border: 1px solid var(--rule);
  background: var(--bg-2);
  font-family: var(--mono); font-size: 12px;
  color: var(--ink-2);
  letter-spacing: 0.02em;
  margin-top: 20px;
}
.scholar .num {
  font-family: var(--serif); font-size: 24px;
  color: var(--accent); font-weight: 500;
  letter-spacing: -0.02em;
}
.scholar .label {
  font-size: 10.5px; text-transform: uppercase;
  letter-spacing: 0.1em; color: var(--ink-3);
  display: block; margin-top: 2px;
}